Claude Fable 5.1 Solves the Cyphral Distich, a 370-year-old cipher
Claude Fable 5.1 solved Sir Thomas Urquhart's 370-year-old Cyphral Distich cipher, recovering a hidden royalist prayer for Charles II.
Vals AI reports that Claude Fable 5.1 solved the Cyphral Distich, a 64-number cryptogram from Sir Thomas Urquhart's Logopandecteision unsolved since 1653, in 44 minutes using 176k tokens with no human hints. The key insight was that the cipher's key was the book itself: each number indexes a word in the corresponding Proquiritation, taking the first letter, yielding 'O GOD UPHOLD KING CHARLS THE SECOND AND MAKE HIM THE SUPREME RULER OF THIS LAND'. The model also deciphered the larger Cyphral Octastich (285 numbers) from The Jewel (1652) using page-based word indexing, recovering all but nine letters of a royalist prayer. The puzzle had been listed among Klaus Schmeh's Top 50 unsolved encrypted messages.
- Cipher solved in 44 minutes, 176k tokens, zero human interjections.
- Key was internal: numbers index words in the 32 Proquiritations; take first letters.
- Plaintext is a Royalist prayer for Charles II, historically consistent with Urquhart's politics.
- Model also cracked the 285-number Cyphral Octastich from The Jewel (1652), all but nine letters.
From the original article
6 min read at vals.ai
We gave Claude Fable 5. 1 an open task: solve Sir Thomas Urquhart’s Cyphral Distich. It appears to have actually solved it, and the solution is quite embarrassing for humans in hindsight.
By u1hcw9nx · vals.ai
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